Advances in the management of malignant mesothelioma

Ribonucleases of different origins with a wide spectrum of medicinal applications

Ribonucleases (RNases) are a type of nucleases that catalyze the degradation of RNA into smaller components. They exist in a wide range of life forms from prokaryotes to eukaryotes. RNase-controlled RNA degradation is a determining factor in the control of gene expression, maturation and turnover, which are further associated with the progression of cancers and infectious diseases. Over the years, RNases purified from multiple origins have drawn increasing attention from medical scientists due to their remarkable antitumor properties. In this review, we present a brief summary of the representative RNases of fungal, bacterial, plant, and animal origins and outline their potential medicinal value in the treatment of tumor and AIDS. Among them, the most clinically promising RNases are mushroom RNases, Binase and Barnase from bacteria, ginseng RNases, and Onconase from frog (Rana pipiens). Fast developing protein engineering of RNases, which display more potent cytotoxic activity on and greater selectivity for malignant cells, has also aroused the interest of researchers. The multiple anti-cancer mechanisms of RNases are also included. To sum up, these inspiring studies unveil a new perspective for RNases as potential therapeutic agents.

Electrolyte and Fluid Transport in Mesothelial Cells

Mesothelial cells are specialized epithelial cells, which line the pleural, pericardial, and peritoneal cavities. Accumulating evidence suggests that the monolayer of mesothelial cells is permeable to electrolyte and fluid, and thereby govern both fluid secretion and re-absorption in the serosal cavities. Disorders in these salt and fluid transport systems may be fundamental in the pathogenesis of pleural effusion, pericardial effusion, and ascites. In this review, we discuss the location, physiological function, and regulation of active transport (Na(+)-K(+)-ATPase) systems, cation and anion channels (Na(+), K(+), Cl(-), and Ca(2+) channels), antiport (exchangers) systems, and symport (co-transporters) systems, and water channels (aquaporins). These secretive and absorptive pathways across mesothelial monolayer cells for electrolytes and fluid may provide pivotal therapeutical targets for novel clinical intervention in edematous diseases of serous cavities.

Preoperative Evaluation of Patients With Malignant Pleural Mesothelioma: Role of Integrated CT-PET Imaging

Malignant pleural mesothelioma (MPM) is an uncommon neoplasm arising from mesothelial cells of the pleura. The prognosis is poor with a median survival of 8 to 18 months after diagnosis. Multimodality regimens combining chemotherapy, radiotherapy, immunotherapy, and surgery are being used more frequently in patient management. Extrapleural pneumonectomy is the surgical treatment of choice in 10% to 15% of patients who present with resectable disease and is reported to prolong survival. Accurate staging is important to distinguish patients who are resectable from those requiring palliative therapy. Integrated computed tomography-positron emission tomography (CT-PET) increases the accuracy of overall staging in patients with MPM and significantly improves the selection of patients for curative surgical resection. Specifically, CT-PET detects more extensive disease involvement than that shown by other imaging modalities and is particularly useful in identifying occult distant metastases. This article reviews aspects of imaging performed in the initial staging of patients with MPM according to the International Mesothelioma Interest Group staging system and will emphasize the appropriate role of CT-PET imaging in determining the T, N, and M descriptors.

Pemetrexed-cisplatin combination in mesothelioma

Despite the desperate struggle for improvement in the therapy of malignant pleural mesothelioma in previous decades, no standard therapy could be established. Pemetrexed (Alimta), a new multitargeted antifolate, showed significant antitumor activity in combination with cisplatin compared with cisplatin alone in patients with unresectable pleural mesothelioma. Furthermore, this improved efficacy was transformed into a significant symptomatic benefit. These data led to the approval of the drug by the US Food and Drug Administration and recently by the European Medicines Evaluation Agency for this combination in malignant pleural mesothelioma, and consequently founded the first standard of treatment in this disease. This review reflects the development of chemotherapy in malignant pleural mesothelioma, discusses the results of the EMPHACIS trial, and outlines further developments for pemetrexed-containing regimens in malignant pleural mesothelioma.

Integrated computed tomography-positron emission tomography in patients with potentially resectable malignant pleural mesothelioma: Staging implications

BACKGROUND

Integrated computed tomography-positron emission tomography imaging with coregistration of anatomic and functional imaging data may improve the accuracy of malignant pleural mesothelioma staging. We evaluate the use of integrated computed tomography-positron emission tomography in patients with malignant pleural mesothelioma who are being considered for extrapleural pneumonectomy.

METHODS

Twenty-nine patients with malignant pleural mesothelioma who were judged to be candidates for extrapleural pneumonectomy after clinical and conventional radiologic evaluation underwent whole-body integrated computed tomography-positron emission tomography and pathologic staging. Two reviewers blinded to the results of clinical and pathologic staging retrospectively evaluated computed tomography, positron emission tomography, and coregistered computed tomography-positron emission tomography images. Staging was performed according to the International Mesothelioma Interest Group TNM staging system. Histopathology and/or results of further radiologic evaluation or follow-up served as the reference standard.

RESULTS

Integrated computed tomography-positron emission tomography provided additional information in 11 of 29 patients that precluded extrapleural pneumonectomy. The overall tumor stage was correctly classified in 21 of 29 patients. The tumor stage was correctly determined in 15 of 24 patients, 6 of whom had T4 (nonresectable) disease. The node stage was accurately determined in 6 of 17 patients. Extrathoracic metastases not identified by routine clinical and conventional radiologic evaluation were detected in 7 of 29 patients and were found to be diffuse (n = 2) or solitary (n = 5).

CONCLUSIONS

Integrated computed tomography-positron emission tomography increases the accuracy of malignant pleural mesothelioma staging and is important in determining the appropriate therapy in patients being considered for extrapleural pneumonectomy.

Phase II Study of a Liposome-Entrapped Cisplatin Analog (L-NDDP) Administered Intrapleurally and Pathologic Response Rates in Patients With Malignant Pleural Mesothelioma

Purpose

To determine pathologic response rates to liposome-entrapped cis-bisneodecanoato-trans-R,R-1,2-diaminocyclohexane platinum(II) (L-NDDP) administered intrapleurally in patients with malignant pleural mesothelioma.

Patients and Methods

Thirty-three patients with malignant pleural mesothelioma and free-flowing pleural effusions received intrapleural L-NDDP once every 3 weeks at a dose of 450 mg/m2. Thoracoscopic evaluation with pleural biopsies was performed before therapy and then after every two cycles. The primary end point was pathologic response as determined by thoracoscopic biopsy.

Results

After at least two cycles, post-treatment pleural biopsy analysis was negative in 14 patients for a pathologic response rate of 42% (95% CI, 25% to 61%). Median survival was 11.2 months. There were three treatment-related deaths secondary to peritonitis, cellulitis at the thoracoscopy site, and empyema. Grade 3 nonhematologic toxicities included infection, fever, dyspnea, and anorexia, which occurred in five (15%), one (3%), one (3%), and one (3%) patients, respectively. There were no grade 4 nonhematologic toxicities. Grade 3 or 4 neutropenia, thrombocytopenia, and anemia occurred in five (15%), three (9%), and two (6%) patients, respectively. Two patients with pathologic responses subsequently underwent pleural decortication. Both surgical specimens revealed residual tumor in regions that were not in direct communication with the pleural space.

Conclusion

Intrapleural L-NDDP therapy in this patient population is feasible with significant but manageable toxicity. Although pathologic responses are highly encouraging, areas of mesothelioma that are not in direct communication with the pleural space will evade drug exposure and limit efficacy in some patients. The optimal role of intrapleural L-NDDP therapy currently remains to be determined.

Pemetrexed Therapy for Malignant Pleural Mesothelioma

OBJECTIVE:

To review pemetrexed, a novel multi-targeted antifolate agent.

DATA SOURCES:

A literature search was conducted (1985–September 2004) using MEDLINE and CANCERLIT. Recent abstracts from the American Society of Clinical Oncology were also included, along with the manufacturer's information. Key words were pemetrexed, LY-231514, Alimta, multi-targeted antifolate, malignant pleural mesothelioma.

STUDY SELECTION AND DATA EXTRACTION:

Relevant information on pharmacology, pharmacokinetics, and safety and efficacy of pemetrexed from clinical trials was selected.

DATA SYNTHESIS:

Pemetrexed inhibits folate metabolism and purine/pyrimidine synthesis. Based on Phase I and II trials, pemetrexed has antitumor activity in solid tumors such as lung, colorectal, and cervical. A pivotal Phase III study in patients with malignant pleural mesothelioma (MPM) demonstrated survival superiority of pemetrexed—cisplatin regimen versus cisplatin.

CONCLUSIONS:

Pemetrexed is a promising new drug for the treatment of solid malignancies, most notably MPM.

Volume-regulated Cl- channels in human pleural mesothelioma cells

Anion channels in human mesothelial and mesothelioma cell lines were characterized by patch-clamp and biomolecular approaches. We found an outwardly rectifying anionic current which was inactivated at positive voltages and inhibited by extracellular adenosine 5'-triphosphate (ATP). Mesothelial and mesothelioma cells behaved differently concerning current inactivation properties. Inactivation is more pronounced and has a steeper onset in mesothelial cells. Different reversal potentials, in asymmetrical Cl(-) solutions, that could be attributed to a different selectivity of the channel, have been observed in the two cell lines. Mesothelioma cell single-channel analysis indicates that the number of the same active anion channel (3-4 pS) increased under hypoosmotic conditions. Immunocytochemistry experiments showed the presence of ICln protein in the cytosol and in the plasma membrane. Western blot analysis revealed an increase of ICln in the membrane under hypotonic conditions, an event possibly related to the activation of Cl(-) channels.